Suppose we want to estimate the risk of getting (hence dying from) a
disease-inducing-serving of beef during the current "Mad Cow Scare" in
the U.S. To do this, we could estimate the risk of getting a
disease-inducing-serving of beef during the British Mad Cow Epidemic.
Clearly, by doing this we are only interested in estimating a WORST CASE
SCENARIO, and we should keep this in mind.
This is because the number of cows infected in the U.S. is clearly much
lower than the number of cows that were infected during the British
epidemic, and this is extremely likely to remain so (due largely to our
current awareness of how to stop the disease's spread and our will to
stop it).

Also, I feel it is difficult to estimate the U.S. situation. It seems
possible that the public is not hearing about every
BSE case. One reason for this is that BSE is fairly rare even in cows and
only one in, at most, 1700 cows is being
tested in the U.S. Also, U.S. beef producers saw what happened in Canada.
It seems unlikely that they would want themselves and our country to
suffer the economic consequences associated to reporting every possible
case. All this makes estimating the US
number challenging, and perhaps the British number will
suffice for our purposes.

Hence we must ask, "What is our goal?". My
goal is to find out whether the chance of getting CJD from
tainted meat is low.
Hence if the British number is low, then it will certainly serve my
purposes. We found that this chance is about 1/10^8, which
is plenty low for me.